For many kinds of shoes, studs are used to improve traction. For example, with a soccer shoe or a golf shoe, studs are used to penetrate the grass surface on which the shoe is used, thereby preventing the shoe from sliding.
Shoes with studs that can be releasably fastened thereto are desirable for several reasons. First, differently shaped studs may be selected and used under different conditions. For example, one type of stud may be used where the ground is dry and another type of stud may be used where the ground is wet. Second, if a stud is worn out, it may be individually replaced, as opposed to replacing the entire sole or shoe.
In some cases, cylindrically-shaped threaded studs are used. For example, cylindrically-shaped threaded studs are sometimes used with soccer shoes. A threaded extension on an upper portion of the stud is screwed into a corresponding threaded opening of the sole.
Higher quality studs, however, are not symmetric like the cylindrically-shaped threaded studs, but rather have an oblong shape. The oblong shape of the stud, together with the orientation of the stud, is optimized for the respective position of the stud on the sole. Such a stud cannot be fastened to the sole by threading.
Furthermore, threading a stud to the sole is very time-consuming. This is problematic where, for example, all the studs of a shoe need to be replaced quickly during a soccer game or a golf tournament, because of changing ground conditions.
Different approaches have been suggested to overcome these difficulties. The special properties of studs, however, limit the number of available solutions. For example, the special properties of studs prevent one from using solutions used for releasably fastening other sole elements as solutions for releasably fastening studs. For example, due to the extremely small volume of a stud, or its receptacle, it is difficult to transfer solutions for the releasable attachment of heels, known from U.S. Pat. Nos. 3,977,095 and 5,133,138, the disclosures of which are hereby incorporated herein by reference in their entireties, to the releasable fastening of studs.
A successful approach for quickly fastening studs to a sole is disclosed in Applicant's U.S. Pat. No. 6,421,937, the disclosure of which is hereby incorporated herein by reference in its entirety. The stud in that document includes a moveable hook that can be shifted by slightly rotating a bolt arranged at the backside of the stud. In rotating the bolt, the hook engages a corresponding recess of the sole and anchors the stud to the sole with a positive fit.
U.S. Pat. No. 6,260,292, the disclosure of which is hereby incorporated herein by reference in its entirety, discloses another example of a releasable stud that does not require threads to fasten/release the stud to/from a sole. A spring mechanism, which includes a ball, locks the stud inside a receptacle of the sole. To release the stud, a special tool is inserted into an opening of the stud and used to separate the stud from the spring mechanism.
In theory, the above discussed stud constructions can substantially reduce the time needed to replace a complete set of the studs, in comparison to studs that require threads. In practice, however, experiences are quite different. For example, dirt adhering to the stud can render the operation of the above described mechanisms difficult. As such, a fast replacement of a set of studs is not always possible. Furthermore, releasable studs of known construction often unintentionally loosen, or even detach, from the sole.
It is, therefore, an object of the present invention to provide a stud that can be reliably and quickly released, even under the most adverse conditions, from a shoe sole, but that does not, at the same time, unintentionally loosen from the shoe sole. A further object of the present invention is to provide a shoe, in particular a soccer shoe, having at least one such stud.